Various structures with peripheral plates or walls containing a liquid component were previously known. For example, a liquid component may be filled between two parallel or near-parallel surfaces and, in such a case, the liquid component is present in a continuous form. The two plates may be edge sealed first with fill holes for subsequent filling of the liquid component. Alternatively, the liquid component may be dropped on one of the two plates (before or after application of the edge sealing adhesive), followed by placing a second plate on top of the first plate to contain the liquid component between the two plates. In some cases, spacers may be present in the continuous liquid phase to control the distance between the two plates. However, such a continuous liquid phase structure suffers certain disadvantages. For example, it lacks structure integrity and depth control, especially when the plates are flexible substrates. In addition, this type of structure is not format flexible for production and, if hard surface plates are involved, batch manufacturing is required which results in low production efficiency.
It is also possible to divide a liquid component into small compartments, for example, by microencapsulation. Individual droplets are wrapped by a wall material to form discreet compartments and such compartments are arranged between two parallel or near-parallel surfaces. There are numerous examples of microencapsulation of a liquid component for different types of applications. In the display field, for example, there are encapsulated electrophoretic displays and encapsulated cholesterol liquid crystal displays. In the pharmaceutical field, drugs may be encapsulated for controlled release. In the imaging field, dye and UV curable monomers may be encapsulated for light/pressure induced imaging development. In this approach, the performance of an encapsulated product or device often depends on the size distribution of the microcapsules. It could be challenging to control the size of the microcapsules to be within a desired range. In addition, the capsule wall usually does not provide good mechanical support for structural integrity, especially with flexible substrates. Material selection is another issue with the microencapsulation technique. In many cases, extra chemical(s) are necessary to stabilize the dispersed phase; the extra chemical(s), however, could be detrimental to the final product.
U.S. Pat. No. 6,930,818 and related patents and patent applications describe a microcup structure for monochrome or multi-color electrophoretic displays. An electrophoretic display device is formed when the microcups are filled with an electrophoretic fluid comprising charged pigment particles dispersed in a dielectric solvent or solvent mixture. U.S. Pat. No. 6,795,138 and related patents and patent applications disclose a liquid crystal display, also utilizing the microcup structure. The liquid crystal composition filled in the microcups may further comprise one or more guest dye(s), in particular, dichroic dye(s). US Patent Application Publication No. 2005-0012881A describes a display device which can display a 3-dimensional image and such a display device is formed when the microcups are filled with an optically active electrophoretic dispersion. US Patent Application Publication No. 2006-0139724 discloses an electrodeposition or electrochromic display device which is formed when the microcups are filled with an electrolyte fluid or an electrochromic fluid. The contents of all of the patents and patent applications referred to above are incorporated herein by reference in their entirety.